Today foam pads are accepted by the general public for family use depending on their appropriate softness or hardness. Where a foam pad is used as a mattress, upon lying down on the mattress, different portions of the body exert different pressures on the mattress. Therefore, a foam mattress with a uniform degree of hardness fails completely to satisfy the comfort level required by the body. If a relatively soft foam mattress is selected, then the middle portion of the body feels comfort, while the support provided for the head and feet of the body thereby appears to be insufficient. On the other hand, by selecting a relatively hard foam mattress, although the amount of support for the head and feet of the body is sufficient, the middle portion of the body is caused to feel hard and uncomfortable. Furthermore, the degree of softness or hardness of the foam is set by differently adjusting the ratios among various substances contained in the raw materials. One solution is to splice together at least three pieces of foam having different densities. The foam pieces at the head and foot of the mattress are harder than the piece of foam in the middle of the mattress.
Forming a mattress by slicing foam pieces having different degrees of hardness, however, complicates the manufacturing process and adds to the cost of the mattress. A method is sought for making a zoned foam mattress that does not require gluing together sliced pieces of foam to form the zones of different hardness.